1. Field of the Invention
This invention relates to the treatment of diseases of the respiratory system and associated parts of the anatomy, such as the heart, and has particular reference to apparatus for controlling the administration of aerosolized medication into the lungs of a patient.
2. Description of the Prior Art
Respirator machines, such as the well-known intermittent positive pressure breathing machine (IPPB), are extensively used in the treatment of patients having lung or allied diseases, such as asthma, emphysema, heart trouble, etc. Such machines have an air outlet which may be connected through a suitable breathing tube to a mouth-piece held in the patient's mouth. Included in the machine is a highly sensitive control device which senses inhalation by the patient, and the resulting negative air pressure, as referenced from the ambient atmospheric pressure, causes the machine to apply a positive pressure flow of air through a T-connection or the like to the mouthpiece to assist the patient during such inhalation phase of each breathing cycle. The machine is also normally responsive to the control device upon sensing negative pressure to apply positive air pressure to the inlet port of a medication nebulizer. The outlet of the nebulizer is connected to an inlet branch of the T-connection. When air passes through the T-connection to the patient's lungs, it causes an aspiration effect which, combined with positive pressure applied to the nebulizer inlet, causes the nebulizer to nebulize a quantity of liquid medication which is admitted to the mouthpiece and is thus introduced into the patient's lungs. During exhalation, the resulting positive pressure developed in the breathing tube causes the control device to disable the nebulizer.
Although the above system is generally satisfactory, it is highly desirable that those patients who are strong enough to carry on their natural breathing functions be allowed to do so while still receiving nebulized medication from the nebulizer. In such cases, the breathing tube is usually removed so that the patient can breath directly to and from the atmosphere through the mouthpiece and T-connection, and the IPPB machine is replaced by a suitable source of pressurized air or oxygen. Therefore, the medication will be nebulized and inhaled during the inhalation phase of the breathing cycle. However, since the machine will continuously apply a positive pressure to the inlet of the nebulizer, much of the medication is wasted since during the exhalation phase of the breathing cycle it is blown out into the atmosphere. Such waste is aggravated by the fact that the period of exhalation is normally of longer duration than the period of inhalation.
Of prime importance in this regard is the fact that it is generally highly desirable to measure the amount of medication entering the patient's lungs or to apply a specific measured amount of such medication. However, with the aforementioned system, the amount cannot be accurately measured since an unknown amount is wasted and therefore the actual amount entering the patient's lungs can only be estimated.
It therefore becomes the principal object of the present invention to provide means for applying medication to a patient's lungs during the inhalation phase only of a breathing cycle while allowing free breathing of the patient to and from the atmosphere without applying positive pressure to the lungs.
Another object is to provide a means for accurately measuring the amount of medication applied to a patient's lungs while permitting free breathing of the patient to and from the atmosphere.
Another object is to utilize an intermittent positive pressure breathing machine and a nebulizer controlled thereby to apply medication to a patient's lungs during inhalation only while permitting free breathing of the patient to and from the atmosphere.